Source Citation

Abstract

Objective

To determine the usefulness of chest radiography for diagnosing increased left ventricular
(LV) preload or reduced ejection fraction (EF).

Data sources

Studies were identified using MEDLINE (1966 to February 1995) with the keywords heart
failure, x-ray, or radiograph; bibliographies of review articles, primary articles,
and textbooks; investigators' files; and by contacting authors of studies.

Study selection

Studies were selected if they compared chest radiographic findings with an acceptable
diagnostic standard for heart failure (reduced EF or increased LV preload). Studies
were excluded if >80% of the patients had valvular heart disease.

Data extraction

Data were extracted in duplicate on patient numbers and characteristics, definitions
of abnormal findings, sensitivity and specificity of radiographic findings, diagnostic
standard (LV preload or EF), and methodologic criteria (interpreter training and blinding,
film technique, timing and clinical stability between radiography and diagnostic standard).

Main results

29 studies met selection criteria. Chest radiographs were compared with LV EF in 10
studies, LV preload in 18 studies, and both in 1 study. Sensitivity, specificity,
and likelihood ratios for a positive (LR+) and negative (LR-) test result are listed
in the Table. Bayesian analysis found that chest radiography can only exclude heart
failure (post-test probability < 5%) and a decreased EF in patients who are asymptomatic
and can never confirm heart failure or a reduced EF (post-test probability > 95%).

Conclusions

The radiographic findings of redistribution and cardiomegaly are most effective for
diagnosing increased left ventricular preload and reduced ejection fraction, respectively.
Neither finding alone, however, has adequate diagnostic utility for left ventricular
dysfunction.

Commentary

Many cardiac disorders manifest themselves as LV systolic dysfunction, from subtle
and subclinical dysfunction to overt congestive failure. The history and physical
examination are the first step in identifying LV dysfunction and often its cause.
Cardiac imaging is commonly used to confirm, exclude, or assess the severity of LV
dysfunction. In a high-technology world of imaging options (ultrasonography, radionuclides,
angiography, computed tomography, and magnetic resonance imaging), the relatively
inexpensive, familiar, and widely available chest radiograph continues to be frequently
used.

The review by Badgett and colleagues delineates the sensitivity and specificity of
chest radiography in the setting of suspected LV dysfunction. Although the authors
did a careful study with excellent statistical methods, 3 caveats should be observed.
First, as the authors indicated, they evaluated individual radiographic signs in isolation,
whereas clinicians usually use clusters of findings from the history, physical examination,
electrocardiogram, and chest radiograph to make diagnoses, which is probably a more
powerful approach. Second, the criterion standards used in the studies varied in the
definition of abnormality (e.g., criteria for abnormal EF ranged from < 35% to
< 50%), potentially adding additional "noise" to the data. Third, the authors
identified patients in whom the radiographic signs could confirm or exclude increased
preload or LV dysfunction (patients with high or low pretest probability, respectively).
In patients in whom LV dysfunction is almost certainly present or absent, chest radiography
is unlikely to substantively alter the post-test probability. It is for patients with
intermediate pretest probability (e.g., patients with dyspnea of uncertain origin
after myocardial infarction) in whom chest radiography may yield diagnostically important
information by altering the post-test probability of disease. Future research could
focus on identifying radiographic and clinical clusters for diagnosis in patients
with intermediate risk.

Chest radiography is best used when the clinician wishes to estimate cardiac size
and configuration and the state of the pulmonary vasculature with 1 examination. When
detailed data on LV size and function are required, chest radiography should be supplanted
by echocardiography or other quantitative, noninvasive imaging methods.